The next generation wireless communication system under active research aims a system capable of transmitting various kinds of information such as video and wireless data, being evolved from the initial system providing voice-oriented services. The fourth-generation wireless communication currently under development subsequent to the third-generation wireless communication aims to support high speed data transmission with 1 Gbps (gigabits per second) data rate in the downlink and 500 Mbps (megabits per second) in the uplink. The main objective of wireless communication system is to provide a plurality of users with reliable communication means independent of their location and mobility. However, any wireless communication channel always reveals non-ideal characteristics such as path loss, noise, fading due to multipath, inter-symbol interference (ISI), or Doppler Effect due to mobility of user equipment (UE). Various technologies are under development to overcome non-ideal characteristics of wireless communication channels and improve reliability thereof.
Moreover, data capacity for cellular wireless systems is ever increasing according to the introduction of machine type communication (MTC) and the advent and deployment of various devices such as smart phones and tablet PCs. Various technologies are under development to meet the needs for high data capacity. For example, carrier aggregation (CA) technology and cognitive radio (CR) technology are good examples of an effort to utilize frequency bandwidth more efficiently. Also, multi-antenna technology, multi-base station collaboration technology, a direct communication system, etc. to increase data capacity within limited frequency bandwidth are being studied.
In order to improve performance of a wireless communication system, coordinated multipoint (CoMP) transmission has been proposed. CoMP is usually renamed as coordinated-multiple-input-multiple-output (co-MIMO), collaborative MIMO, network MIMO, etc. CoMP is expected to increase cell-edge UE performance and enhance average sector throughput. In general, inter-cell (ICI) reduces cell-edge UE performance and average sector throughput under multi-cell environment with frequency reuse factor 1. To mitigate ICI, the simple passive technique (i.e., fractional frequency reuse (FFR) with UE specific power control) was employed in order to provide reasonable throughput performance for the cell-edge UEs in the interference-limited environment. Instead of reducing frequency resource usage per cell, it is more beneficial to reuse ICI as a desired signal or mitigate the ICI.
For downlink case, CoMP schemes can be categorized as follows:
Joint Processing (JP): data is available at each point in CoMP cooperating set.
Joint Transmission (JT): PDSCH is transmitted from multiple points (part of or entire CoMP cooperating set) at a time. Data to a single UE is simultaneously transmitted from multiple transmission points, e.g. to (coherently or non-coherently) improve the received signal quality and/or cancel actively interference for other UEs.
Dynamic point selection (DPS): PDSCH is transmitted from one point at a time (within CoMP cooperating set).
Coordinated Scheduling/Beamforming (CS/CB): Data is only available at serving cell (data transmission from that point) but user scheduling/beamforming decisions are made with coordination among cells corresponding to the CoMP cooperating set.
For uplink case, CoMP reception implies reception of the transmitted signal at coordination among multiple, geographically separated points and CoMP schemes can be categorized as follows:
Joint reception (JR): Transmitted signal of PUSCH is received at multiple reception points.
Coordinated Scheduling/Beamforming (CS/CB): PUSCH is received only at a one point but user scheduling/beamforming decisions are made with coordination among cells corresponding to the CoMP cooperating set.
CoMP is currently an essential consideration in LTE (long term evolution)-A based on 3GPP (3rd Generation Partnership Project) TS (Technical Specification) Release 10. As disclosed in 3GPP TS 36.211 V10.4.0 (2011-December) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 10)”, the physical channel in LTE-A can be divided into PDSCH(Physical Downlink Shared Channel) and PDCCH(Physical Downlink Control Channel), which are downlink channel, and PUSCH(Physical Uplink Shared Channel) and PUCCH (Physical Uplink Control Channel), which are uplink channel. The specification of the present invention proposes a method for determining starting position of PDSCH in CoMP environment.